The central theme of this program project is the determination of the mechanisms by which distinct subsets of memory CD4 T cells provide protective memory against pulmonary infections, with particular emphasis on Thi and Th17 subsets generated during influenza virus or Mycobacterium tuberculosis infections. Proiect 1 (Dr. Swain) will study how distinct helper subsets of CD4 effectors progress to form protective CD4 memory T cell populations in response to immunization or infection with influenza viruses. Proiect 2 (Dr. Dutton) will study how distinct cytotoxic subsets of CD8 effectors progress to form protective Cb8 memory T cell populations in response to immunization or infection with influenza viruses. Proiect 3 (Dr. Bradley) will examine the role CD4 T cell migration plays in the generation and protective function of anti-viral CD4 memory T cell subsets. Finally, Proiect 4 (Dr. Cooper) will investigate the relationship between CD4 T cell subsets in generating protective CD4 memory T cells against MTb. This program as a whole is designed to determine the mechanisms involved in generating protective T cell immunity to pulmonary pathogens, with a strong focus on defining distinct T cell subsets that correlate cytokine polarization profiles with protective functions like migration to the site of infection, cytotoxicity of infected cells, and B cell helper activities. Although each project will approach this question differently, and will address different aspects of CD4 T cell immune responses to pathogen-derived antigens, the goal of this Core is to produce the reagents, viruses, and mouse strains required by the investigators to complete the proposed studies in a well controlled and cost effective manner. Each of the projects in this Program propose experiments that will require polarizing cytokines, monoclonal antibodies, and/or fusion proteins produced by Core B. The projects of Swain, Dutton, and Bradley propose to use influenza viruses, as well as all of the recombinant and purified influenza virus proteins produced by Core B. The projects of Drs. Swain and Bradley would be greatly facilitated with the generation of a flu-specific TCR Tg CD4 mouse strain on the C57BL/6 background. RELEVANCE (See instructions): The goal of Core B is to produce the high quality and critical reagents, viruses, and mouse strains that will facilitate the success of all principal investigators involved in this program.